Carrie Underwood‘s son Isaiah Michael is celebrating being one year older by showing it actually is easy being green.

In honor of her older child turning 4, the county star — who recently welcomed her second baby, son Jacob Bryan, with husband Mike Fisher — showed off the festive Muppets-themed cake she served at Isaiah’s special celebration, which was held a few days before his actual birthday on Wednesday.

“Ummm … @iveychildersand @iveycakestore have outdone themselves once again!” Underwood wrote on Instagram Sunday, alongside a series of photos showing off the elaborate, colorful creation.

The sweet treat consisted of a giant replica of Kermit the Frog resting atop a cake shaped like the number 4, which was also covered in polka dots and various beloved characters from the Muppets franchise like Miss Piggy, Rowlf, Animal, Gonzo, Beaker and the Swedish Chef.

Along the base of the cake, a message proclaimed, “Happy birthday Isaiah,” along with a “MOST WANTED” stamp — a reference to the birthday boy’s favorite movie at the moment, Muppets Most Wanted.

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“Isaiah loves the Muppets and his favorite movie right now is Muppets Most Wanted,” explained the “Cry Pretty” singer, 35. “He wanted a ‘most dangerous frog’ cake and he most certainly got one!”

Praising the pastry further, she wrote, “And it tasted as delicious as it looked! Thanks for making his birthday celebration extra special!” before adding the hashtags “#MyBestieIsABaker #IveyCake #Yum.”

So far, this is the only photo Underwood has shared from her son’s birthday celebration — his first since becoming a big brother on Jan. 21.

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Before her Cry Pretty tour kicks off in May, the American Idol alum is spending time with her family of four at home in Tennessee, enjoying every moment.

“They’re total homebodies,” a source previously told PEOPLE. “They rarely leave their home at night and love the outdoors and often go for walks.”

“Carrie lives a very quiet life. They take Isaiah fishing, to the zoo and to farms so he can learn about animals,” added the insider. “They very much live a farm life and seem to love it.”

The proud mama shared the first photos of her newborn last month as she simultaneously shared the good news that she had officially become a mother for the second time.

“Jacob Bryan Fisher entered the world in the wee hours of the morning on Monday … his mom, dad and big brother couldn’t be happier for God to trust them with taking care of this little miracle!” Underwood wrote alongside a photo gallery of herself, Fisher and proud big brother Isaiah holding onto Jacob.

“Our hearts are full, our eyes are tired and our lives are forever changed. Life is good … ” she added.

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Shortly after Underwood shared Jacob’s birth announcement, Fisher shared a celebratory post of his own, which touched on their tough pregnancy journey.

“Jacob Bryan Fisher! You are a gift from our Lord! The last few years [has had] its challenges and it makes this moment even more sweet,” the former professional ice-hockey player, 38, captioned an Instagram photo, which showed baby Jacob nuzzled on his chest.

“We didn’t know if Izzy would ever have another sibling but we learned through it all that God is in control and his timing is perfect. He is good all the time even in the difficult times that are hard to understand,” Fisher continued, adding the hashtags “#grateful” and “#miraclebaby.”